Name: Gravitational Potential Energy
Uploaded: 2019-07-19
Duration: 9 min 10 s
Description: The energy possessed by a body because of its position in a gravitational field is known as Gravitational Potential Energy. Let’s learn about it in detail in...

Question

The figure below shows a simple pendulum of mass 200 g and length 1 m. It is moved from position A to B. What is potential energy of the pendulum at B? Now pendulum is released from position B. What is its energy at A? What is the speed at A?

Accepted Answer

Given,

Mass of the pendulum: $= 200 g = 0.2 kg$
Height to which bob is raised: $= 10 cm = 0.1 m$
Potential energy at B $= mgh = 0.2 \times 10 \times 0.1 = 0.2 J$
Now at position A i.e the mean position of the pendulum
Potential energy at A $= 0$
By the law of conservation of energy, we have
Total energy initial = Total energy final

Therefore, energy of the pendulum bob at position A $= 0.2 J$
Also, $KE = \frac{1}{2} {mv}^{2}$
Hence, $\frac{1}{2} {mv}^{2} = 0.2$

$\Rightarrow 0.2 = \frac{1}{2} \times 0.2 \times v^{2}$

$\Rightarrow v^{2} = 2$

$\Rightarrow v = \sqrt{2} = 1.414 {ms}^{- 1}$

Therefore, the speed of pendulum bob at position A is $1.414 {ms}^{- 1}$

The figure below shows a simple pendulum of mass 200 g and length 1 m. It is moved from position A to B. What is potential energy of the pendulum at B? Now pendulum is released from position B. What is its energy at A? What is the speed at A?

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